mast ding! re-drill spreader holes???

[briangsmith]

argghhh! if it ain't one thing...

during trailering last fall one spreader half apparently
took a load (yes, I should have removed spreaders prior
to trailering- sigh)- I have a nickel-sized ding where one
corner of the aluminum spreader 'baseplate' (?) dug into
the actual mast.

My question is this. The obvious fix to me would be to
re-drill all four holes and simply move the spreaders up,
or down, 4" or 5". But will this cause an appreciable change
in the load? To the spreaders, wire, mast...??

bgs
E-25 c/b
homer, alaska

 

[Emerald]

Hi,


I had dimples on my E-27's mast from the spreader attachment. As I looked at repair alternatives, making a collar was the solution. Here's a web page I put together on it that takes you all the way through the process:

http://home.comcast.net/~ericson-yachts/dimple/dimple_repair.html

I would absolutely not change the hieght of the spreaders unless you could get a naval architect to OK it. I think you would find loading throughout the rig changes quite a bit for messing with the geometry of the triangles formed by your spreaders.


-David
Independence 31
Emerald

 

[briangsmith]

thanks david... other opinions here? i mean, ok, just how
much can it alter overall loads to move the spreaders up
6" on a 30' mast?? i dont' know, and that's why i'm a' askin'!

bgs

 

[Guy Stevens]

Its not loading, its geometry and construction

OK, First a plug for one of my best friends books..."The Riggers Apprentice"..... Brion Toss available at www.briontoss.com.

The first thing that happens if you were to move the spreaders, is that you move them off of the area of the mast that was hopefully manufactured to take the side loads from the spreaders and not bend dimple etc. There should be compression tubes, and or some other reinforcements in that area....

The second issue is that spreaders exist for the purpose of making the angle that the shrouds meet the top of the mast greater if you move them up you do change this angle. Now generally since we are looking for a bigger angle this would seem to help with the rigging system, but lets look at the forces a little.

6" up on the mast, doesn't seem like a lot, but it can be enough of a difference to break the mast in half... (Which counts as worse than a ding where do your lower stays connect? Somewhere about where the spreaders are right? Funny thing about that, the side pressure of the spreaders keeps the mast in column at as close a spot as we can to the loads from the lower stays. This is so we don't break the mast in half with the lower stays.

The best way to begin to understand the complexity of this system is to go out for a chocolate shake. Get a really big long straw, a couple of sailing friends (You will probably have to buy them a shake too, cause they are always broke), and start having people be the spreaders etc. The straw will bend and flex in response to your table top rigging and show you what small changes can make huge differences.

In summary, it might be able to be moved, however I would have a competent rigger take a look at the situation and go from there. Where are you?? Being in the rigging circle I know people in a variety of places that I might be able to recommend. But not in Homer Alaska....

Guy

 

[briangsmith]

thanks guy- i just recently purchased brion's book- yes, a great
reference resource. lisa at port townsend rigging -- who you also
probably know! -- is currently replacing all of my standing rigging,
and i have an e-mail out to them re. this (newly discovered) issue.

the configuration of the E-25 c/b ('78 hull #383) has a very basic
set of spreaders -- horizontal, no upwards cant at all -- two bolts
with compression post right into the mast, no sleeve, bracket or
other such reinforcement. hey, i guess it's worked for going on
30 years... (boat is new to me last summer, i have one season
sailing in on her)

i'll wait to hear back from PT rigging, but, again, really appreciate
expert opinions, and anecdotal experience, here as well~

bgs